Decatur is the largest city and county seat of Morgan County in the U.S. state of Alabama. Nicknamed "The River City," it is located in northern Alabama on the banks of Wheeler Lake along the Tennessee River. The population was 57,938 at the 2020 census.

The Tennessee Valley is the drainage basin of the Tennessee River and is largely within the U.S. state of Tennessee. It stretches from southwest Kentucky to north Alabama and from northeast Mississippi to the mountains of Virginia and North Carolina. The border of the valley is known as the Tennessee Valley Divide. The Tennessee Valley contributes greatly to the formation of Tennessee's three legally recognized sectors.